The objective of the research project is to study roles of inherited adenosine deaminase deficiency in the pathogenesis of immunodeficiency disease. Two cytotoxic purine nucleosides, adenosine and deoxyadenosine, accumulate to relatively high levels in patients with severe combined immunodeficiency disease associated with adenosine deaminase deficiency. We propose a novel hypothesis that these cytotoxic purine nucleosides originates from macrophages in the bone marrow and lymphoid organs. This hypothesis will be tested using in vitro culture model systems, with macrophages from various tissues of mice and a potent adenosine deaminase inhibitor, deoxycoformycin. Two additional nucleosides, deoxycytidine and thymidine, are identified in the mouse peritoneal macrophage culture medium. We will determine whether these nucleosides have any immunoregulatory functions by assaying for growth inhibitory effects of the culture medium of macrophages maintained in the presence of deoxycoformycin, using mouse lymphoma cells as the assay system. We will also derive mutant sublines lacking adenosine deaminase from a mouse lymphoma line and a mouse macrophage-like line, in order to be able to establish appropriate culture model systems for the disease. Furthermore, we will study purine and pyrimidine metabolism in both primary cultures and the permanent cell line of macrophages. The results will elucidiate the relationships between nucleic acid metabolism of macrophages, their scavenging functions and their immunoregulatory roles in healthy as well as in diseased individuals.